The Micro-Temperatures of the Peaks and Valleys of Sliding Rough Surfaces

2018 ◽  
Vol 883 ◽  
pp. 53-62 ◽  
Author(s):  
Shin Yuh Chern ◽  
Jeng Haur Horng ◽  
Cheng Han Tsai ◽  
Hung Jung Tsai
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Rough Surfaces ◽  
Chemical Processes ◽  
The Finite Element Method ◽  
Precision Control ◽  
Sliding Speed ◽  
Surface Failure ◽  
Contact Surfaces ◽  
Transient Thermal

The surface micro-temperature of sliding, rough bodies is an important factor affecting contact properties, such as chemical reactions of automatic injectors for medicine and chemical processes and surface failure of micro-and macro-devices. In this work, the Finite Element Method is used to analyze the micro-temperature of the peaks and valleys of multiplying asperity sliding contact surfaces. The affecting parameters include pressure, roughness, sliding speed, Peclet number, and thermal conductivity of rough surfaces. Analysis results showed that the effects of the studied parameters are different to those of peak and valley temperatures. While pressure increased, the increasing rate of the temperature rise parameter of valleys was larger than those of peaks. The temperature rise of peaks increased as roughness increased. On the contrary, the temperature rise of valleys decreased as roughness increased. Sliding speed and thermal conductivity played the most important roles in affecting the maximum micro-temperature rise. The temperature rise difference between peaks and valleys was almost proportional to thermal conductivity, and was inversely proportional to sliding speed for all cases. This transient thermal analysis enables precision control of interface micro-temperature for micro-moving devices.

Stress Analysis of a Tire Under Vertical Load by a Finite Element Method

1977 ◽  
Vol 5 (2) ◽  
pp. 102-118 ◽  
Author(s):  
H. Kaga ◽  
K. Okamoto ◽  
Y. Tozawa
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computer Program ◽  
Temperature Rise ◽  
Strain Energy ◽  
Internal Stresses ◽  
Vertical Load ◽  
The Finite Element Method ◽  
Internal Temperature ◽  
Element Method

Abstract An analysis by the finite element method and a related computer program is presented for an axisymmetric solid under asymmetric loads. Calculations are carried out on displacements and internal stresses and strains of a radial tire loaded on a road wheel of 600-mm diameter, a road wheel of 1707-mm diameter, and a flat plate. Agreement between calculated and experimental displacements and cord forces is quite satisfactory. The principal shear strain concentrates at the belt edge, and the strain energy increases with decreasing drum diameter. Tire temperature measurements show that the strain energy in the tire is closely related to the internal temperature rise.

Measurement of Thermal Conductivity of a Flexible Substrate

2014 ◽  
Author(s):  
Vivek Vishwakarma ◽  
Ankur Jain
Keyword(s):  
Thermal Conductivity ◽  
Analytical Model ◽  
Flexible Substrate ◽  
Thermal Response ◽  
Experimental Methodology ◽  
Plastic Substrate ◽  
The Past ◽  
Thin Plastic ◽  
Transient Thermal ◽  
Transient Thermal Response

A number of past papers have described experimental techniques for measurement of thermal conductivity of substrates and thin films of technological interest. Nearly all substrates measured in the past are rigid. There is a lack of papers that report measurements on a flexible substrate such as thin plastic. The paper presents an experimental methodology to deposit a thin film microheater device on a plastic substrate. This device, comprising a microheater line and a temperature sensor line is used to measure the thermal conductivity of the plastic substrate using the transient thermal response of the plastic substrate to a heating current. An analytical model describing this thermal response is presented. Thermal conductivity of the plastic substrate is determined by comparison of experimental data with the analytical model. Results described in this paper may aid in development of an understanding of thermal transport in flexible substrates.

Thermal Conductivity in Thin Silicon Nanowires with Rough Surfaces by Molecular Dynamics Simulations

2010 ◽  
Author(s):  
Xueming Yang ◽  
Albert C. To ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Silicon Nanowires ◽  
Rough Surfaces ◽  
Thin Silicon ◽  
Dynamics Simulations

scholarly journals Thermal Analysis of AlGaN/GaN HEMTs Considering Anisotropic And Inhomogeneous Thermal Conductivity

2021 ◽  
Author(s):  
Yao Li ◽  
Zixuan Zheng ◽  
Qun Li ◽  
Hongbin Pu
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Power Dissipation ◽  
Thermal Characteristics ◽  
Maximum Temperature ◽  
Base Temperature ◽  
Initial Growth ◽  
Boltzmann Transport ◽  
Growth Interface ◽  
Anisotropic Thermal Conductivity

Abstract To examine the differences of thermal characteristics introduced by material thermal conductivity, anisotropic polycrystalline diamond (PCD) and GaN are analyzed based on the accurate model of grain sizes in the directions of parallel and vertical to the interface and an approximate solution of the phonon Boltzmann transport equation. Due to the space-variant grain structures of PCD, the inhomogeneous-anisotropic local thermal conductivity, homogeneous-anisotropic thermal conductivity averaged over the whole layer and the typical values of inhomogeneous-isotropic thermal conductivity are compared with/without anisotropic GaN thermal conductivity. The results show that the considerations of inhomogeneous-anisotropic PCD thermal conductivity and anisotropic GaN thermal conductivity are necessary for the accurate prediction of temperature rise in the GaN HEMT devices, and when ignoring both, the maximum temperature rise is undervalued by over 16 K for thermal boundary resistance (TBR) of 6.5 to 60 m2K/GW at power dissipation of 10 W/mm. Then the dependences of channel temperature on several parameters are discussed and the relations of thermal resistance with power dissipation are extracted at different base temperature. Compared with GaN, SiC and Si substrates, PCD is the most effective heat spreading layer though limited by the grain size at initial growth interface.

Evaluating Thermal Cycling Fatigue Resistance for LED Chip-on-Board Applications

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 000706-000737
Author(s):  
Ravi M. Bhatkal ◽  
Ranjit Pandher ◽  
Anna Lifton ◽  
Paul Koep ◽  
Hafez Raeisi Fard
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Cycle ◽  
Metal Core ◽  
Creep Fatigue ◽  
Cte Mismatch ◽  
Thermal Cycling Fatigue ◽  
Transient Thermal ◽  
The Impact

LED chip-on-board applications typically involve assembling an LED die stack directly on to a high thermal conductivity substrate such as a Metal Core PCB. If solder is used for die-substrate attach for such chip-on-board applications, one needs to consider the CTE mismatch between the die stack and the MCPCB and its impact on thermal cycle-induced creep fatigue of the solder material. This paper presents a methodology to compare relative performance of different solder materials with varying thermo-mechanical properties, and compare the impact of CTE mismatch and temperature swings on transient thermal properties and relative reliability of the solder attach materials. Implications for LED chip-on-board applications are discussed.

Detection of grouting defects in prestressed tendon ducts using distributed fiber optic sensors

2019 ◽  
Vol 19 (4) ◽  
pp. 1273-1286
Author(s):  
Shilin Gong ◽  
Xin Feng
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Fiber Optic ◽  
Detection Efficiency ◽  
Fiber Optic Sensors ◽  
Detection Methods ◽  
Experimental Program ◽  
Accurate Identification ◽  
Equivalent Thermal Conductivity ◽  
Abnormal Temperature

To compensate for the shortcomings of the existing point detection methods for grouting defects in prestressed tendon ducts, such as low detection efficiency, stringent detection environment, and easy omission of grouting defects, this article presents a distributed detection approach to detect the grouting defects in tendon ducts. The main objective of the research pertained to the development of a method for accurate identification and location of grouting defects and qualitative evaluation of the size of grouting defects using distributed fiber optic sensors with active heating. Using the thermal analysis of grouting defects in the tendon duct and the research on distributed fiber optic sensors measurement characteristics, our work proposed a method for identifying and locating grouting defects and explored the effect of the grouting defect length and the grouting compactness on the temperature rise of distributed fiber optic sensors. The feasibility of the proposed approach is evaluated through an experimental program. The experimental program involved use of heating distributed fiber optic sensors for the distributed measurement of temperature after the heating and detection of grouting defects in tendon ducts in a concrete beam. The results indicate that distributed fiber optic sensors can monitor the temperature distribution of the tendon duct during a temperature rise in real time. Grouting defects in the tendon duct can be quickly detected and located by identifying temperature anomalies in the temperature contour of the distributed fiber optic sensors. Furthermore, there is a linear relationship between the defect length and the abnormal temperature length on the distributed fiber optic sensors, and the defect length can be identified based on the abnormal temperature length obtained by the measurement. Plane-equivalent thermal conductivity can be used to evaluate the grouting compactness of the tendon duct. When the grouting compactness is greater than 70%, the smaller the plane-equivalent thermal conductivity is, the lower the grouting compactness is. The plane-equivalent thermal conductivity is basically the same when the grouting compactness is less than 70%.

Experimental and Theoretical Modeling of the Effective Thermal Conductivity of Rough Steel Spheroid Packed Beds

2003 ◽  
Vol 125 (4) ◽  
pp. 693-702 ◽  
Author(s):  
G. Buonanno ◽  
A. Carotenuto ◽  
G. Giovinco ◽  
N. Massarotti
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Solid Mechanics ◽  
Packed Bed ◽  
Elementary Cell ◽  
Upper And Lower Bounds ◽  
Packed Beds ◽  
The Finite Element Method ◽  
Two Phase ◽  
Experimental Apparatus

The upper and lower bounds of the effective thermal conductivity of packed beds of rough spheres are evaluated using the theoretical approach of the elementary cell for two-phase systems. The solid mechanics and thermal problems are solved and the effects of roughness and packed bed structures are also examined. The numerical solution of the thermal conduction problem through the periodic regular arrangement of steel spheroids in air is determined using the Finite Element Method. The numerical results are compared with those obtained from an experimental apparatus designed and built for this purpose.

The Thermal Load and Ablation Mechanism of Piston Subjected to Detonation

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Jian Gao ◽  
Anren Yao ◽  
Chunde Yao
Keyword(s):  
Surface Layer ◽  
Thermal Ablation ◽  
Thermal Load ◽  
Heat Dissipation ◽  
The Finite Element Method ◽  
Reciprocating Engine ◽  
Ablation Mechanism ◽  
Transient Thermal ◽  
Short Time ◽  
Heat Released

Abstract The piston in reciprocating engine would be badly ablated under severe knock. However, the mechanism of the detonation-induced thermal ablation of piston is still unclear. A detonation bomb device (DBD) was used to measure the thermal load of piston under detonation. A test specimen mounted on the detonation bomb acts as a piston to bear the detonation load. Transient thermal numerical analysis was performed using the finite element method. Temperature of the specimen and in-cylinder pressure were collected synchronously. A method for estimating wall heat flux under detonation was proposed. Results showed that the heat received by the specimen accounts for about 20.9% of the total heat released by the mixture in this research. Under continuous detonations, the heat of the surface layer could not be conducted to the interior in a short time, leading to a rapid rise in surface temperature. The overall temperature rise of the specimen limits the heat dissipation of the specimen surface layer, resulting in the specimen being ablated by the over-temperature and over-pressure. Piston thermal ablation by detonation is verified and reappeared in the detonation bomb. The thermal load of the piston is largest under theoretical equivalent ratio.

Thermal-Mechanical Contact of a Sphere on a Layered Surface

2010 ◽  
Author(s):  
Wenping Song ◽  
Andrey Ovcharenko ◽  
Guangyu Zhang ◽  
Frank E. Talke
Keyword(s):  
Layer Thickness ◽  
Coating Thickness ◽  
Temperature Rise ◽  
Material Properties ◽  
Mechanical Deformation ◽  
The Other ◽  
Mechanical Contact ◽  
Other Hand ◽  
Transient Thermal

The effect of coating thickness is investigated during transient thermal-mechanical contact between a sphere and a layered surface. The range of coating thicknesses studied was from 0.001≤t/R≤0.1, where t is the coating thickness and R is the radius of the contacting sphere. It was found that for the range of coating thickness and material properties investigated, the coating thickness has only a small effect on the mechanical deformation of the interface. On the other hand, the layer thickness has a large effect on the temperature rise of the interface.

A Tiny Detector Made of a Self-Heated Thermistor for Determining Thermal Conductivity of Biomaterials in Temperature Range 233~313K

2002 ◽  
Author(s):  
H. F. Zhang ◽  
S. X. Cheng ◽  
L. Q. He ◽  
A. L. Zhang ◽  
Y. Zheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carotid Artery ◽  
Temperature Rise ◽  
Measurement Errors ◽  
Homogeneous Medium ◽  
Standard Samples ◽  
Temperature Range ◽  
A New Technique ◽  
Maximum Measurement

In this paper, a new technique, using a tiny thermistor with 0.3~0.5mm in diameter to determine thermal conductivity of biomaterials in wide temperature range, has been developed. Based on steady spherical heat transfer in an infinite homogeneous medium, thermal conductivity of the measured medium can be determined by power applied and temperature rise of the thermistor. Compared with recommended values, maximum measurement errors of standard samples, aqueous glycol and CaCl2 solutions, water and ice, are 5.1% in temperature range 233~313K. The thermal conductivities of rabbit’s liver, kidney, heart and carotid artery in temperature range 233~293K are determined. Error caused by measurement parameters, effects of the finite scale of the measured medium and the decoupler between the thermistor and the medium are analyzed.

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